package storage

import (
	"context"
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/google/uuid"
	"github.com/jackc/pgx/v5"
	"github.com/jackc/pgx/v5/pgconn"
	"github.com/jackc/pgx/v5/pgxpool"

	"github.com/alchemistkay/guestguard/internal/domain"
)

type EventRepo struct {
	pool *pgxpool.Pool
}

func NewEventRepo(db *DB) *EventRepo {
	return &EventRepo{pool: db.Pool}
}

type CreateEventParams struct {
	HostID      uuid.UUID
	Name        string
	Slug        string
	EventDate   time.Time
	Venue       string
	MaxCapacity int
	Settings    map[string]any
	Status      domain.EventStatus
}

func (r *EventRepo) Create(ctx context.Context, p CreateEventParams) (*domain.Event, error) {
	settings := p.Settings
	if settings == nil {
		settings = map[string]any{}
	}
	settingsJSON, err := json.Marshal(settings)
	if err != nil {
		return nil, fmt.Errorf("marshal settings: %w", err)
	}

	const q = `
        INSERT INTO events (host_id, name, slug, event_date, venue, max_capacity, settings, status)
        VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
        RETURNING id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at
    `
	row := r.pool.QueryRow(ctx, q,
		p.HostID, p.Name, p.Slug, p.EventDate, p.Venue, p.MaxCapacity, settingsJSON, p.Status,
	)
	ev, err := scanEvent(row)
	if err != nil {
		var pgErr *pgconn.PgError
		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
			return nil, domain.ErrSlugTaken
		}
		return nil, err
	}
	return ev, nil
}

func (r *EventRepo) Get(ctx context.Context, id uuid.UUID) (*domain.Event, error) {
	const q = `
        SELECT id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at
        FROM events WHERE id = $1
    `
	ev, err := scanEvent(r.pool.QueryRow(ctx, q, id))
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, domain.ErrEventNotFound
		}
		return nil, err
	}
	return ev, nil
}

func (r *EventRepo) List(ctx context.Context, hostID uuid.UUID, limit, offset int) ([]*domain.Event, error) {
	if limit <= 0 || limit > 200 {
		limit = 50
	}
	if offset < 0 {
		offset = 0
	}

	var (
		rows pgx.Rows
		err  error
	)
	if hostID == uuid.Nil {
		rows, err = r.pool.Query(ctx, `
            SELECT id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at
            FROM events
            ORDER BY created_at DESC
            LIMIT $1 OFFSET $2
        `, limit, offset)
	} else {
		rows, err = r.pool.Query(ctx, `
            SELECT id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at
            FROM events
            WHERE host_id = $1
            ORDER BY created_at DESC
            LIMIT $2 OFFSET $3
        `, hostID, limit, offset)
	}
	if err != nil {
		return nil, err
	}
	defer rows.Close()

	var out []*domain.Event
	for rows.Next() {
		ev, err := scanEvent(rows)
		if err != nil {
			return nil, err
		}
		out = append(out, ev)
	}
	return out, rows.Err()
}

type UpdateEventParams struct {
	Name        *string
	Slug        *string
	EventDate   *time.Time
	Venue       *string
	MaxCapacity *int
	Settings    *map[string]any
	Status      *domain.EventStatus
}

func (r *EventRepo) Update(ctx context.Context, id uuid.UUID, p UpdateEventParams) (*domain.Event, error) {
	const q = `
        UPDATE events SET
            name         = COALESCE($2, name),
            slug         = COALESCE($3, slug),
            event_date   = COALESCE($4, event_date),
            venue        = COALESCE($5, venue),
            max_capacity = COALESCE($6, max_capacity),
            settings     = COALESCE($7, settings),
            status       = COALESCE($8, status),
            updated_at   = now()
        WHERE id = $1
        RETURNING id, host_id, name, slug, event_date, venue, max_capacity, settings, status, created_at, updated_at
    `

	var settingsJSON []byte
	if p.Settings != nil {
		b, err := json.Marshal(*p.Settings)
		if err != nil {
			return nil, fmt.Errorf("marshal settings: %w", err)
		}
		settingsJSON = b
	}

	row := r.pool.QueryRow(ctx, q, id,
		p.Name, p.Slug, p.EventDate, p.Venue, p.MaxCapacity, settingsJSON, p.Status,
	)
	ev, err := scanEvent(row)
	if err != nil {
		if errors.Is(err, pgx.ErrNoRows) {
			return nil, domain.ErrEventNotFound
		}
		var pgErr *pgconn.PgError
		if errors.As(err, &pgErr) && pgErr.Code == "23505" {
			return nil, domain.ErrSlugTaken
		}
		return nil, err
	}
	return ev, nil
}

func (r *EventRepo) Delete(ctx context.Context, id uuid.UUID) error {
	tag, err := r.pool.Exec(ctx, `DELETE FROM events WHERE id = $1`, id)
	if err != nil {
		return err
	}
	if tag.RowsAffected() == 0 {
		return domain.ErrEventNotFound
	}
	return nil
}

type rowScanner interface {
	Scan(dest ...any) error
}

func scanEvent(s rowScanner) (*domain.Event, error) {
	var (
		ev           domain.Event
		settingsJSON []byte
	)
	err := s.Scan(
		&ev.ID, &ev.HostID, &ev.Name, &ev.Slug, &ev.EventDate, &ev.Venue,
		&ev.MaxCapacity, &settingsJSON, &ev.Status, &ev.CreatedAt, &ev.UpdatedAt,
	)
	if err != nil {
		return nil, err
	}
	if len(settingsJSON) > 0 {
		if err := json.Unmarshal(settingsJSON, &ev.Settings); err != nil {
			return nil, fmt.Errorf("unmarshal settings: %w", err)
		}
	} else {
		ev.Settings = map[string]any{}
	}
	return &ev, nil
}